| Edmonds CiCi | ||
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| Here's the CiCi on one of its better flights, this one on September 15, 2007. |
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| At some point later in 2007, I was
flying gliders one evening when I encountered one of the shotgun
ejection charges common in Estes motors a few years ago. The
motor pod separated from the rocket, and I could not find it despite
repeated searches. So I repaired the rocket by building a new motor pod. A short length of BT-20 was used along with a spare nosecone I had. Vent holes were added on either side of the pod to relieve the ejection pressure in hope of preventing damage from another shotgun motor. Normally, the pod is attached directly to the main spar of the airframe. When the shotgun ejection charges would be encountered, the main spar would come apart along its grain. In other words, to make the rocket more resilient, the pod needed to attach in such a way as to strengthen the wood grain, which is best managed by rotating the material 90° to the grain. So some 1/16" balsa was cut into two pylons and attached astride the spar. I swagged the angle as best I could and set it at about 6°. |
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From
the end, it is clear the pylons staddle the main spar. The hope
was that this attachment method would be much stronger against the
shotgun motors. |
| As part of the repair, instead
of putting the launch lug along side the motor pod, it was moved to the
main spar near the middle. The idea was to reduce the amount of
torque imparted to the launch lug due to wind. With the large
rear wing, only a small breeze will impart a significant moment on the lug at
the other end. This causes the lug to bind on the rod making
it hard for the rocket to move. With the lug in the middle, the
binding should be minimized. |
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| With
a new motor pod and launch
lug, I got out the red and black magic markers and prettied up the
rebuilt Cici. Then I took it out for a launch. The idea
behind angling the motor pod is to counter the lift from the canard
during boost so that the rocket climbs fairly straight. I
sometimes will angle the rod to help correct for tendencies either
way. In the case of this launch, I think two things got me - too
much angle in the motor pod, and the rod was angled the wrong
way. In fact, since the rocket had just been repaired, I probably
should have had the rod straight up. In essense, I had a major
brain fart. And paid the price. As soon as it cleared the
rod, it immediately turned toward the gound and power pranged. The rocket was nearly totalled. In fact, all that was salvaged was the motor pod and rear wing. Everything else was trashed. |
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| Starting with the salvaged bits,
I built a new CiCi. Borrowing from my CiCi2 experience, I used a
carbon fiber rod as the main spar. New parts include the forward
pylons and canard, and rear pylon and rudders. Orange dye was used this time. Some of the black used on the salvaged parts is still visible on the main wing. |
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| The pod was attached to the new pylons. Kraft paper was used to reinforce the joints. |
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| The pylons straddle the main spar at the canard. The launch lug is now back on the forward section. |
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| Lacking the laser cut tabs of the original, kraft paper was used to reinforce the inside and outside of the joints between the rudders and main wing. |
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| A wrap of light fiberglass secures the spar to the pylon on the aft wing. |
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Here's
a liftoff shot of the new
CiCi. The trajectory off the rod looks a little scary. But
the only comment in my notes was that it needed more noseweight.
I guess I have some work to do. But at least it's still in one
piece  |
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12-28-2008 |
